package javaBase.nowcoder.HJ37_S_统计每个月兔子的总数;

import java.io.*;
public class Main{
    public static void main(String args []) throws Exception{
        BufferedReader br = new BufferedReader(new InputStreamReader(System.in));
        int n = Integer.parseInt(br.readLine());
        System.out.println(fe(n));
    }
    public static  int fe(int n){
        if (n == 0){
            return 0;
        }
        if (1 == n){
            return 1;
        }
        if(2 == n){
            return 1;
        }
        return fe(n-1) + fe(n-2);
    }
}
